Digital broadcast systems have undergone rapid development and deployment in recent years due, at least in part, to their ability to efficiently distribute large numbers of high-fidelity video and/or audio programs, as well as other digital services or programs, over a large geographic region. For example, in the case of satellite-based digital television and audio broadcast systems, little, if any, land-based infrastructure (e.g., ground stations, cable lines, etc.) is needed to provide services to subscribers on a world-wide basis. As a result, such satellite-based systems enable digital broadcasters and content providers to develop markets for their programs and/or services in remote and/or underdeveloped regions of the world in a cost-effective manner.
In general, regardless of whether a digital broadcast system uses one or more satellites, cable transmission lines, ground-based wireless transmission stations, or any combination thereof, such a system enables users to receive high-fidelity video and/or audio programs, as well as user-interactive features or tools such as, for example, pictographic program guides, grid-based guides, etc. that enable users to plan and carry out program consumption activities. Digital broadcast systems typically transmit one or more high-bandwidth signals, each of which is typically composed of a stream of data or data packets having a plurality of video, audio and/or other digital programs or content multiplexed therein. A number of well-known data compression techniques (e.g., audio/video content compression techniques), transmission protocols and the like are typically employed to generate and transmit a multi-program data stream or bitstream, which is commonly referred to as a transport stream. In particular, digital television programming is typically transmitted according to a standard promulgated by the Advanced Television Standards Committee (ATSC). The ATSC standard is a comprehensive standard relating to the conveyance of digital television signals. Under the ATSC standard, video information associated with a program is encoded and compressed according to the well-known Moving Pictures Expert Group-2 (MPEG-2) standard and audio information associated with the program is encoded and compressed according to the well-known AC-3 standard. As a result, an ATSC data stream or bit stream contains video information in the form of MPEG-2 packets and audio information in the form of AC-3 packets. However, other digital transmission protocols, data compression schemes and the like may be used instead.
In the case of freely available digital audio/video content or programming, users must have a television adapted to receive and process digital television signals (e.g., a high definition television). In the case of purchased digital audio/video content or programming, subscribers typically have a digital decoder unit which, in the case of a digital video or television system, is commonly referred to as a “set-top box,” that receives and processes multi-program data streams or transport streams and outputs video and audio signals to a television, video monitor, speakers, etc. for consumption by the user. In particular, the set-top box can, based on subscriber commands, extract data packets associated with a particular program or portion of audio/video content from a particular data stream or transport stream, decode those extracted data packets and send video and/or audio signals to a television, video monitor, digital radio, etc. for consumption by a user.
As is the case with analog content providers and broadcasters, digital content providers and broadcasters (e.g., digital television broadcasters, digital audio broadcasters, etc.) often desire to verify the transmission and/or to meter (i.e., monitor) the consumption of the audio/video content or programs and/or other services provided to subscribers. In this manner, a broadcaster can generate broadcast verification information and/or audience program consumption behavior or patterns. Audience consumption behavior or patterns may be used in conjunction with demographic information to develop ratings information, to improve targeted marketing or advertising campaigns, to improve the types of programs or audio/video content and/or services and the times at which those programs and/or services are delivered to consumers, to assess the value of a particular time slot and program for purposes of determining what advertisers should pay for usage of that time slot, etc.
With known analog television metering systems, viewing records or other viewing information is typically collected from a group of statistically selected households. As with digital broadcast systems, each of the statistically selected households has a data logging and processing unit (i.e., “home unit” or “site unit”). The site unit is usually coupled to a variety of attachments that provide inputs to the site unit or that receive outputs from the site unit. For example, an analog system may include a frequency detector to detect the local oscillator frequency of a television to identify the channel to which the television is currently tuned. Also, for example, a people counter, may be located in the viewing space of the television and may be in communication with the site unit, thereby enabling the site unit to actively or passively detect the identities of the persons currently viewing programs presented by the television.
The site unit usually processes its inputs, including the inputs from its attachments, to produce viewing records. The viewing records typically contain audio/video content or program identification information (i.e., information that can be used to identify a particular program or portion of audio/video content, such as channel information obtained from the frequency detector) and audience information. The audience information may include the numbers and/or identities of persons viewing a particular program, demographic information, etc. The viewing records may be generated on a periodic basis (i.e., at fixed time intervals) or may be generated in response to a change in an input such as, for example, a change in the identities or number of persons viewing the television, a change in the channel tuning information (i.e., a channel change), etc. With known analog systems, each viewing record typically contains channel information such as a station or channel number and a time (e.g., a date and time of day) at which the channel was viewed. Of course, viewing records may contain other information such as the identities of viewers present at the viewing time.
The site unit collects a quantity of viewing records and transmits collected viewing records, usually daily, to a collection site, such as central office or data processing facility, for further processing or analysis. The data processing facility receives viewing records from site units located in some or all of the statistically selected households and analyzes the viewing records to ascertain the viewing behaviors of a particular household or a particular group of households selected from all participating households. Additionally, the central data processing facility may generate viewing behavior statistics and other parameters indicative of viewing behavior associated with all of the participating households.
To generate viewing behavior information from viewing records, the central office or data processing facility compares reference data such as a list of programs (i.e., a schedule of television programming or program lineup) to the viewing records. In this manner, the data processing facility can determine which programs were viewed by matching the times and channel information in the viewing records to the programs associated with those same times and channels in the program schedule or lineup. Such a matching process can be carried out for each of the viewing records received by the data processing facility, thereby enabling the data processing facility to reconstruct what programs were watched by all participating households and the times at which the programs were watched.
However, known analog program metering systems (such as the television program verification and metering systems discussed above) are not suitable for use with digital broadcast systems. For example, the frequency detector attachment described above is not suitable for detecting digital video channel information because digital television systems use a data packet extraction process within a set-top box to retrieve audio/video data associated with a particular program, while the television tuner is typically allowed to remain on a single channel (e.g., typically channel 2 or 3). As a result, the local oscillator frequency of the television tuner is not indicative of (i.e., does not necessarily correspond to) the digital television channel currently being consumed. Thus, known analog program metering systems are not suitable for use with digital broadcast systems. More generally, known analog program metering systems cannot be used to detect the identity of broadcast digital programs, thereby preventing analog monitoring systems from being used to generate verification information and/or viewing records that can be processed to determine digital program consumption behavior.
To enable the tracking of viewing records, some digital broadcasters enable the identification of digital broadcast programs at home sites and one or more reference sites by inserting digital program identification information and/or other data in the video and/or audio bitstream(s). The inserted digital data is commonly referred to as audience measurement data, which may include signal identification codes (i.e., digital codes that are uniquely associated with respective audio/video content portions or programs), date information, time information, consumer identification information, etc. The insertion of audience measurement data at the distribution system headend or broadcast station is commonly referred to as an active audio/video content identification process because the system headend or broadcast station actively modifies (i.e., inserts data into) the transmitted bitstreams or transport streams.
By actively inserting data into audio/video bitstreams in this manner, digital broadcasters enable the identification of digital audio/video content and the viewing behavior of persons viewing digital broadcasts to be readily determined. In particular, the site units associated with individual homes sites may be configured to extract the inserted audio/video content identification codes from known portions or locations within a received bitstream and to use the extracted information to form, for example, viewing records. In turn, viewing records may be further analyzed at each of the home sites and/or at one or more collection or central processing sites to generate viewing behavior information, ratings data, etc.
Typically, known active data insertion techniques insert digital data within each of the video and/or audio signals that make up the one or more programs (i.e., video and/or audio programs) being transmitted by the broadcast station before the individual video and/or audio signals are compressed and multiplexed to form a single multi-program bitstream or transport stream. However, because the digital data are inserted in an uncompressed domain (i.e., within the individual uncompressed audio/video signals), multiple digital data insertion devices (e.g., one for each uncompressed program bitstream) are typically required. This requirement for multiple digital information insertion devices is undesirable because it increases the complexity and operational costs associated with headend or broadcast stations.
Another difficulty that results from inserting digital data into individual uncompressed program signals is that subsequent compression operations (e.g., compression encoding) may corrupt and/or eliminate some or all of the inserted data. As is known, signal compression techniques usually provide a substantial reduction in the quantity of data needed to reproduce a video image and/or an audio signal, but do so at the expense (i.e., the loss) of at least some data or information. Thus, if compression operations corrupt the inserted digital data, the home site and/or a central data processing or collection facility may not be able to accurately identify audio/video content.
Still another difficulty that results from inserting digital codes or audience measurement data into individual uncompressed audio/video content signals is that the association between the inserted data or information and the program into which the data is inserted is limited. In particular, the inserted data may be associated with only the video portion of a program or only the audio portion of that same program, but not both the video and audio portions. This lack of association is further complicated by the fact that a digital broadcast station may redefine the position (e.g., the sub-channel or minor channel number) of an uncompressed video and/or audio program within the compressed domain, or may delete one or more video and/or audio programs from a program lineup.